Log Message:
Update to 2.5.8; add test target.
Changes since 2.5.7:
- bugfixes: XPath, XInclude, file/URI mapping, UTF-16 save (Mark
  Itzcovitz), UTF-8 checking, URI saving, error printing (William Brack),
  PI related memleak, compilation without schemas or without xpath (Joerg
  Schmitz-Linneweber/Garry Pennington), xmlUnlinkNode problem with DTDs,
  rpm problem on , i86_64, removed a few compilation problems from 2.5.7,
  xmlIOParseDTD, and xmlSAXParseDTD (Malcolm Tredinnick)
- portability: DJGPP (MsDos) , OpenVMS (Craig A. Berry)
- William Brack fixed multithreading lock problems
- IPv6 patch for FTP and HTTP accesses (Archana Shah/Wipro)
- Windows fixes (Igor Zlatkovic,  Eric Zurcher), threading (Stéphane
  Bidoul)
- A few W3C Schemas Structure improvements
- W3C Schemas Datatype improvements (Charlie Bozeman)
- Python bindings for thread globals (Stéphane Bidoul), and method/class
  generator
- added --nonet option to xmllint
- documentation improvements (John Fleck)